Digital transactions for the delivery of media files

ABSTRACT

An incomplete/partly corrupted media file is delivered ‘in the clear’; in addition, a delta file is delivered to users meeting access control criteria which, when combined with the incomplete/partly corrupted parts allows a complete and uncorrupted version of the media file to be re-constructed. The method allows, in one implementation, a secure music purchase system to operate over digital radio: for example, the start of a song when played over the radio is usually deliberately talked over and the end cut short to prevent listeners being able to record a complete copy. With the present system, this practice can continue, but listeners can also purchase the missing or corrupted sections to enable them to possess a complete and uncorrupted version for playback.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority of PCT Application No.PCT/GB01/03069 filed Jul. 9, 2001 and British application GB 0016695.9filed Jul. 8, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of digital transactions,particularly to transactions in which copies of digital media files areacquired. The media files are typically music files (but can be anyother type of media file) and the delivery mechanism may be, but is notlimited to, a digital radio transmission such as DAB (Eureka-147) or theInternet.

2. Description of the Prior Art

Conventional analogue radio systems (such as FM or AM) can causesignificant channel noise to be introduced into the transmitted audiosignal payload; the payload is in any event generally rendered into theanalogue domain before being allowed to modulate the carrier. As aresult, analogue systems are inappropriate vehicles for selling musicdirectly, since any recording will be significantly compromised withrespect to the (in these days, usually digital) original which can bepurchased through conventional music stores (e.g., as a CD) or throughthe Internet (e.g., as an MP3 file).

However, with the introduction of digital radio systems (e.g., theEureka-147 standard adopted throughout the UK, Europe and elsewhere) thepossibility of the direct sale of digital music ‘over the air’ appears,at first, to become a significant possibility. This is because:

-   -   Digital sources are used. The source music is encoded using a        digital compression system (e.g., Musicam (a slight variant of        MPEG1layer-2 and MPEG2-layer-2 audio) for Eureka-147 DAB).        Therefore, there is little, if any, perceptible difference        between the material put to air and that which can be purchased        by the user though the normal commercial channels, as described        above.    -   The received signal will be, for most users, an exact copy of        that which was transmitted. Modern digital radio systems all        contain some form of forward error correction (FEC). This        involves the addition of structured redundancy to the        transmitted signal so that the receiver can accurately infer the        intended payload message, even in the face of significant        corruption by the channel. Coupled with checksum tests on the        audio, and channel error temporal and frequency decoherence        mechanisms, this means that digital radios tend to have        so-called ‘cliff-effect’ reception—either the received audio is        exactly that which, bit-for-bit, left the studio, or no signal        at all is received. This must be contrasted with analogue radio,        in which most channel corruptions become directly perceptible        within the delivered audio signal.    -   Potential lack of source compression. Analogue radio systems        often artificially compress the source material spectrum in        order to make their signal appear ‘louder’ (useful e.g., for in        car listening where the ambient noise level is high and quiet        passages can be lost). Digital radio systems can (although they        need not) avoid this problem, through the use of mechanisms such        as the Eureka-147 dynamic range control, in which compression is        performed at the receiver end.

These three points, taken together, mean that the digital radio userreceives, essentially, a digital ‘clone’ of the original message. Thisis (minus packaging) what the user would be able to purchase through thenormal channels discussed above, hence the possibility of commercialsale of the material ‘downloaded’ over the air. The commercial sale ofmaterial ‘downloaded’ over the Internet already occurs of course.

However, using radio as the vehicle for the commercial sale of musicturns out not to be practicable using existing known mechanisms, in thegeneral case, for the following reasons:

-   -   Radio stations tend not to transmit all of a particular music        item—for example they will often ‘cut’ the start and ends of        popular music tracks to make them fit a particular play slot.        (This is also a problem with ‘classic request’ channels which        may play only one movement from a classical piece, or worse, a        selection from a single movement).    -   The radio station will often impose corruptions onto the        transmitted item—for example, ‘fades’ at the start and end of a        track, the disk jockey talking over certain parts of a track,        special effects, adverts or jingles overlaid on the track, etc.    -   Even if the above two factors were not a concern, then piracy        would prove problematical for the music vendor. This is because,        in order for the radio to play the track, the music will have to        be transmitted, to all intents and purposes, ‘in the clear’.        However, for security, the track would need to be encrypted,        only to be unlocked by an authorised purchasing key.

SUMMARY OF THE PRESENT INVENTION

In accordance with a first aspect of the present invention, there isprovided a method of delivering a digital media file comprising thefollowing steps:

-   -   (a) dividing a master version of a digital media file into a        first series of time frames and a second series of time frames;    -   (b) delivering the first series of time frames to one or more        users without any form of access control, the first series        capable of being used to form a version of the media file which        is incomplete and/or corrupted;    -   (c) delivering the second series of time frames to one or more        users, the second series capable of being used in conjunction        with the first series to form a version of the media file which        is complete and uncorrupted, in which access to the second        series is only granted to users satisfying defined access        control criteria.

Hence, the method envisages delivering an incomplete/partly corruptedmedia file ‘in the clear’; in addition, a delta file is delivered tousers meeting access control criteria which, when combined with theincomplete/partly corrupted parts allows a complete and uncorruptedversion of the media file to be reconstructed. The method allows, in oneimplementation, a secure music purchase system to operate over digitalradio: for example, the start of a song when played over the radio isusually deliberately talked over and the end cut short to preventlisteners being able to record a complete copy. With the present system,this practice can continue, but listeners can also purchase the missingor corrupted sections to enable them to possess a complete anduncorrupted version for playback. Hence, spontaneous purchasing ofcomplete, played over the air tracks is possible, which is not only veryconvenient for listeners but highly attractive for content owners andradio stations.

In a second aspect, there is a method of receiving a digital media fileat a receiving device, the media file being held at a remote source as amaster version divided into a first series of time frames and a secondseries of time frames; the method comprising the following steps:

-   -   (a) receiving at the receiving device the first series of time        frames, the first series capable of being used by the receiving        device to form a version of the media file which is incomplete        and/or corrupted;    -   (b) receiving at the receiving device the second series of time        frames, the second series capable of being used by the receiving        device in conjunction with the first series to form a version of        the media file which is complete and uncorrupted, in which        access to the second series is only possible if the receiving        device satisfies defined access control criteria.

In a third aspect, there is an apparatus for processing a digital mediafile, the apparatus programmed to:

-   -   (a) divide a master version of a digital media file into a first        series of time frames and a second series of time frames;    -   (b) send the first series of time frames, the first series        capable of being used at a receiving device without any form of        access control to form a version of the media file which is        incomplete and/or corrupted;    -   (c) send the second series of time frames, the second series        capable of being used at the receiving device in conjunction        with the first series to form a version of the media file which        is complete and uncorrupted, in which access to the second        series is only granted to users satisfying defined access        control criteria.

In a forth aspect, there is an apparatus for receiving a digital mediafile, the media file being held at a remote source as a master versiondivided into a first series of time frames and a second series of timeframes; the apparatus programmed to:

-   -   (a) receive the first series of time frames, the first series        capable of being used by the receiving device to form a version        of the media file which is incomplete and/or corrupted;    -   (b) receive the second series of time frames, the second series        capable of being used by the receiving device in conjunction        with the first series to form a version of the media file which        is complete and uncorrupted, in which access to the second        series is only possible if the receiving device satisfies        defined access control criteria.

In a fifth aspect, there is a media file structured into a first seriesof time frames and a second series of time frames; the first seriescapable of being used by a receiving device to form a version of themedia file which is incomplete and/or corrupted; the second series oftime frames capable of being used by the receiving device in conjunctionwith the first series to form a version of the media file which iscomplete and uncorrupted, in which access to the second series is onlypossible if the receiving device satisfies defined access controlcriteria.

In a sixth aspect, there is provided a method of selling media files, inwhich the method comprises a method of delivering in accordance with thefirst aspect of the invention, the delivery of the second series of timeframes being paid for by a user.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawing which is a schematic overview of the present invention.

DETAILED DESCRIPTION

The radio implementation operates by identifying the fact that themajority of modern audio encoding systems break information up intoframes in the time domain, (which may or may not be of the same lengthin time as each other but which, without loss of generality, we shallassume in this discussion are of the same length).

Therefore, given a piece of merchantable audio material A, the digitalaudio playout system at the studio can generate a frame-wise compressedversion A₀, A₁, A₂, . . . A_(n−1). Of these n frames, only m<=n will betransmitted, and of these m, only p<=m will be uncorrupted. Assume thatthe studio audio playout system maintains a log of which frames aretransmitted uncorrupted to air, and which are either not sent at all, orare sent with some corruption. Corruption can also arise throughreception errors, which will vary from user to user.

Then the possibility exists, to generate a second stream, generally muchsmaller than the first, consisting of only those n−p un-transmitted oruncorrupted frames (in their original, pristine format), which may beencrypted and sent to air as an additional service. (This is astraightforward task with a system such as Eureka-147 DAB in which themultiplex can be rapidly reconfigured to hold new data or audioservices, in stream or packet mode, provided that an overall payloadlimit is not exceeded, and can even allow data services to be embeddedwithin extra space allocated within the audio frames themselves).

With such a system, the receiver would be able to play the receivedmusic, which, in the normal case, would consist of the m transmittedframes, m−p of which would be corrupt, and n−m of which would bemissing. The user could record this should they so desire, but it would(in the general case where p<m<n) be much less desirable than thegenuine, uncut, unblemished original that could be purchased though theconventional channels discussed earlier.

However, in a receiver equipped with the appropriate decoder module, theuser could record the message transmitted ‘in the clear’, together withthe ‘delta’ stream. This ‘delta’ stream would have been decoded from theappropriate second service discussed above. If desired, he system couldbe configured only to be able to decode the delta stream with theassistance of a purchase authentication device, such as a ‘smart card’,decryption key or Internet authorization.

The receiver would then be able automatically to reassemble the originalpayload, by appending (from the delta stream) any un-transmitted framesinto the received ‘clear’ message, and overwriting any corrupted framesin the ‘clear’ message with their pristine versions (from the deltastream). FIG. 1 is a schematic representation of this system. Generally,the corrupted frames might be deliberately corrupted by the studio; thenthe audio playout log maintains a record of these deliberately corruptedframes so that they can be readily incorporated into the delta stream.In addition, where corruption arises through reception errors (andtherefore differs from receiver to receiver), an individual‘personalised’ delta file, specific to each receiver, can be defined andrequested by a receiver where a back channel is available.

The resulting stream could be node-locked if desired to prevent thepurchased music from being portable (and indeed this facility could beapplied simply by ensuring that the delta frames were node-locked),although generating a fully clear final message would also be an option.Hence, serial copy inhibition can be provided for by making the deltaframes readable only by a specific device, using a unique ID of thatdevice.

The system could also be incorporated within a ‘circular bufferrecording’ unit such that the last q seconds of audio received (togetherwith any appropriate delta files, still in encrypted form) would be heldin store, such that a user would be able to initiate a recording of anitem at some time after it had commenced playing (perhaps even after ithad finished).

This system would yield significant benefits for broadcasters, end usersand music vendors alike, allowing the traditional benefits of radio(e.g., first play of new ‘hit’ songs which are of interest to users andhelp stimulate the market for music vendors) to be turned into asubsequent sale, without either the vendors running a significant riskof music piracy or the users having to suffer a long secondary downloadof music that (for the most part) they have already received. The systemenables music lovers for the first time to spontaneously purchase amusic track, album etc, on hearing that piece of music played on theradio.

Note that this system could also be deployed in a form where the deltafile was downloaded directly via a two-way communications system (e.g.,over a cellular channel, or via the Internet). This system would requirethat the user made a generally short) connection to download the deltafile, but would have the following additional advantages:

-   -   The music vendor could identify and directly authenticate the        user in question, therefore being better able to combat fraud        and offer personalised marketing incentives such as special        offers for regular customers, etc.    -   The user could benefit because their receiver might also request        additional ‘personalised’ delta frames which have been corrupted        due to channel effects (these frames can be detected through        checksum failures if this is supported in the digital radio        system in question).

The system would also be appropriate for use with Internet streaming inplace of digital radio. The system would be appropriate for any mediastream, including video, not limited to audio, although its primaryintended target would be digital radio.

1. A method of delivering a digital media file to a receiving device, comprising the following steps: a) dividing a master version of a digital media file into a first series of time frames and a second series of different time frames; b) delivering the first series of time frames to one or mote users without any form of access control, the first series capable of being used to form a version of the media file which is incomplete and/or corrupted; c) delivering the second series of time frames to one or more said users the second series capable of being re-combined with the first series to form a re-assembled version of the media file which is complete and uncorrupted, in which access to the second series is only granted to users satisfying defined access control criteria; wherein the receiving device automatically records a defined time period of the first series of time frames irrespective of any user selection of a record function of the receiving device; and wherein the defined period is adequate to enable a user to record an entire media work even though the user only selects the record function of the device substantially after commencement of receiving the media work.
 2. The method of claim 1 in which the second series is encrypted.
 3. The method of claim 1 in which any time frames missing and/or corrupted in the first series of time frames are present in an uncorrupted form in the second series.
 4. The method of claim 1 in which the second series is transmitted together with the first series.
 5. The method of claim 1 in which the second series is transmitted separately from the first series in response to a user request.
 6. The method of claim 5 in which the user request specifies any first frames which are corrupted.
 7. The method of claim 1 in which the media file is a music file broadcast over digital radio.
 8. The method of claim 1 in which the media file is a media file streamed over the Internet.
 9. The method of claim 1 in which the version of the media file which is complete and uncorrupted is structured to be reproducible only at a specific user receiving device to prevent serial copying.
 10. The method of claim 9 in which the second series of time frames is node locked to render the version of the media file which is complete and uncorrupted to be reproducible only at a specific user receiving device.
 11. A method of selling media files, in which the method comprises a method of delivering in accordance with claim 1, the delivery of the second series of time frames being paid for by a user.
 12. A method of receiving a digital media file at a receiving device, the media file being held at a remote source as a master version divided into a first series of time frames and second series of different time frames, the method comprising the following steps: a) receiving at the receiving device the first series of time frames, the first series capable of being used by the receiving device to form a version of the media file which is incomplete and/or corrupted; b) receiving at the receiving device the second series of time frames, the second series capable of being re-combined by the receiving device with the first series to form a version of the media file which is complete and uncorrupted, in which access to the second series is only possible if the receiving device satisfies defined access control criteria; wherein the receiving device automatically records a defined time period of the first series of time frames irrespective of any user selection of a record function of the receiving device; and wherein the defined period is adequate to enable a user to record an entire media work even though the user only selects the record function of the device substantially after commencement of receiving the media work.
 13. The method of claim 12 in which the second series is transmitted separately from the first series in response to a request from the receiving device.
 14. The method of claim 13 in which the receiving device specifies any first frames which are corrupted.
 15. The method of claim 12 in which the media file is a music file broadcast over digital radio.
 16. The method of claim 12 in which the media file is a media file streamed over the Internet.
 17. The method of claim 12 in which the version of the media file which is complete and uncorrupted is structured to be reproducible only at a specific user receiving device to prevent serial copying.
 18. The method of claim 17 in which the second series of time frames is node locked to render the version of the media file which is complete and uncorrupted to be reproducible only at a specific user receiving device.
 19. An apparatus for processing a digital media file, the apparatus programmed to: a) divide a master version of a digital media file into a first series of time frames and a second series of different time frames; b) send the first series of time frames, the first series capable of being used at a receiving device without any form of access control to form a version of the media file which is incomplete and/or corrupted; c) send the second series of time frames, the second series capable of being re-combined at the receiving device with the first series to form a version of the media file which is complete and uncorrupted, in which access to the second series is only granted to users satisfying defined access control criteria; wherein the apparatus automatically records a defined time period of each of the first and second series of time frames irrespective of any user selection of a record function of the apparatus; and wherein the defined period is adequate to enable a user to record an entire media work even though the user only selects the record function of the device substantially after commencement of receiving the media work.
 20. The apparatus of claim 19 in which the first and second series of time frames are sent to another apparatus located at the same site as the apparatus.
 21. The apparatus of claim 19 in which the first and second series of time frames are sent to another apparatus located remotely from the site of the apparatus.
 22. An apparatus for receiving a digital media file at a receiving device, the media file being held at a remote source as a master version divided into a first series of time frames and second series of different time frames, the apparatus programmed to: a) receive the first series of time frames, the first series capable of being used to form a version of the media file which is incomplete and/or corrupted; b) receive the second series of time frames, the second series capable of being re-combined with the first series to form a version of the media file which is complete and uncorrupted, in which access to the second series is only possible if the receiving device satisfies defined access control criteria; wherein the apparatus automatically records a defined time period of each of the first and second series of time frames irrespective of any user selection of a record function of the apparatus; and wherein the defined period is adequate to enable a user to record an entire media work even though the user only selects the record function of the device substantially after commencement of receiving the media work.
 23. The apparatus of claim 22 in which the second series is transmitted separately from the first series in response to a request from the apparatus.
 24. The apparatus of claim 23 in which the apparatus specifies any first frames which are corrupted.
 25. The apparatus of claim 22 in which the version of the media file which is complete and uncorrupted is structured to be reproducible only at a specific user receiving device to prevent serial copying.
 26. The method of claim 25 in which the second series of time frames is node locked to render the version of the media file which is complete and uncorrupted to be reproducible only at a specific user receiving device. 